Yemenis protest a video clip last month outside the U.S. Embassy in Sanaa. A top Yemeni security official who worked at the embassy was killed Thursday.

Yemenis protest a video clip last month outside the U.S. Embassy in Sanaa. A top Yemeni security official who worked at the embassy was killed Thursday.

Photo: Hani Mohammed, Associated Press

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In this Thursday, Sept. 13, 2012 file photo, Yemeni protestors climb the gate of the U.S. Embassy during a protest about a film ridiculing Islam's Prophet Muhammad, in Sanaa, Yemen. A drive-by shooting that killed a top Yemeni security official who worked at the U.S. Embassy in Sanaa Thursday, Oct. 11, 2012 raises concern that al-Qaida militants here are bouncing back and getting bolder after suffering defeats this year in U.S.-Yemeni military offensive. Al-Qaida has carried out a string of assassinations of top government and military officials, reportedly has a hit list to kill more and has called for attacks on U.S. diplomatic missions.(AP Photo/Hani Mohammed, File) less

In this Thursday, Sept. 13, 2012 file photo, Yemeni protestors climb the gate of the U.S. Embassy during a protest about a film ridiculing Islam's Prophet Muhammad, in Sanaa, Yemen. A drive-by shooting that ... more

Photo: Hani Mohammed, Associated Press

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Yemeni U.S. Embassy worker assassinated

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Sanaa, Yemen --

A Yemeni security investigator at the U.S. Embassy here was shot and killed Thursday by masked men on a motorcycle in the latest assassination by militants of political and security targets in cities across the country.

Yemen officials said the ambush bore the tracings of al Qaeda, which in recent months has intensified its activities in the Yemeni capital after coming under increasing pressure by U.S. drone strikes and offensives by security forces against its redoubts in the nation's south.

The slaying follows last month's storming of the embassy by a mob outraged by an anti-Islam video produced in California that denigrated the Prophet Muhammad. The video ignited a wave of anti-American protests across the Muslim world. Yemen has long been a dangerous country for U.S. interests - a 2008 car bombing at the embassy killed at least 16 people, including militants - and Sanaa, the capital, is an eerie mix of Islamic extremists, tribes, rebels and soldiers loyal to rival factions, including the family of former President Ali Abdullah Saleh.

"After military actions against al Qaeda in the south, the group has declared an open war against the government," said Saeed Ali Obaid Jamhi, an expert on militant groups. "Al Qaeda has a list of those they want to assassinate and at the top of it is the Yemeni defense minister."

Qassem Aqlan was shot Thursday in his car near his house in western Sanaa. The embassy is in the eastern part of the city. Yemen officials described Aqlan as a security liaison officer.

U.S. State Department spokeswoman Victoria Nuland said in a statement that Aqlan "worked as a Foreign Service national investigator at the embassy for the last 11 years. He was a dedicated professional who will be greatly missed." Al Qaeda in the Arabian Peninsula has exploited Yemen's persistent political unrest, especially since demonstrations last year that ultimately forced Saleh, who had ruled the country for 33 years, to step down. The new president, Abed Rabu Mansour Hadi, has welcomed U.S. drone strikes, including those last week that killed about five extremists, and other military assistance in targeting al Qaeda leaders.

U.S. forces are believed to have carried out at least 34 air strikes in Yemen this year, up from 10 the previous year, according to the website Long War Journal, which tracks drone strikes in Yemen and elsewhere.